Electric socket



ELECTRIC SOCKET May 169 Filed Feb, 3' 1957 lmvemtcr: Joseph D Ceeaer,

by ZC-ff H is tt OT`-m ey Patented May 16, 1939 UNITED STATES PATENT OFFICE Joseph D. Ceader, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application February 3, 1937, Serial No. 123,755

14 Claims.

The present invention relates to electric sockets having provisions for preventing short-circuit between the terminals of the socket when the socket is empty. One use of sockets of this type is for Christmas tree lights where the conventional socket is likely to be short-circuited by pieces of tin foil dropping between the exposed terminals of the empty socket.

The object of my invention is to provide an improved construction for sockets of this type and for a consideration of what I believe to be novel in my invention, attention is directed to the accompanying description and the claims appended thereto.

In the accompanying drawing Fig. 1 is an elevation of a socket embodying my invention showing a lamp in the socket; Fig. 2 is a sectional elevation at right angles to Fig. 1 with one-half of the base removed and showing the lamp in the socket; Fig. 3 is a view similar to Fig. 2 with the lamp removed; Fig. 4 is a sectional view similar to Fig. 1 with the lamp removed; Fig. 5 is a sectional elevation of a modication; Fig. 6 is a perspective view of a part oi the socket shown in Fig. 5; and Fig. 7 is an elevation of another modification of my invention.

Referring to the drawing the numeral I indicates a screw shell which serves as one terminal for the socket. The shell is carried within a base which comprises parts 2 and 3 of molded insulating material which are held together by a U shaped spring clip 4 which fits iin the grooves la. The base is split along the axis ci the shell so that the base may be assembled around the shell. One of the arms of the clip 4 is provided,

with a tang 5 and the other arm is provided with a rounded projection 5a which lits into depressions in the parts of the base and prevents easy removal of the clip. From the rounded projection 5a of the clip extends an arm 6 which coopcrates with the base to provide a clip for supporting the socket. This clip is particularly useful in the case of sockets for use on Christmas trees since the clip 6 may be fastened over a branch of the tree.

At the lower end of the base the abutting surfaces of the parts of the base are provided with spaced transverse grooves 1 for clamping a. pair of conductors 8 between the parts of the base. One of the conductors is connected to a contact 9 which serves as the center terminal of the socket. This contact is provided with tangs IIJ (see Fig. 4) which extend on either side of the conductor and are electrically connected thereto by squeezing the tangs together. The other conductor is similarly connected to a contact Il which is adapted to engage the shell I which serves as the other terminal of the socket. The tangs of the contact II extend over both of the conductors but are electrically connected to only the lower conductor. Withthis arrangement the contact Il serves to prevent displacement of the conductors. The conductors li are adapted to form the respective conductors of a string of parallel connected Christmas tree lights.

The center terminal 9 extends through an opening provided by complementary grooves I2 in the parts 2 and 3 oi the base into a recess I3 in the base. 'Ihe contact Il, likewise, extends into the recess I3 through complementary grooves Il formed in the parts of the'base. The grooves I2 and I4 hold the contacts 9 and II in place. The inner surface or the recess I3 is provided with threads Ia which cooperate with the threads I5 on the screw shell I. The friction between the threads Ma and I5 is such that the shell is threaded into and out of the base by a plug I8 threaded into the shell. 'I'hat is, the friction between the threads of the plug I6 and the threads of the shell ls greater than the friction between the threads of the shell and the threads Ila of the base. The lower end oi' the shell I has a smooth portion I'I so that the shell cannot be threaded outward beyond the position shown in Fig. 3. 'I'he contact of the threads Ila of the base with. the smooth portion I1 of the shell provides a stop which limits the outward movement. W'hen the shell is in the outer position, there is a wedging action between the threads Ila and I5 which tends to separate the parts 2 and 3 of the base. 'Ihe pressure exerted by the parts of the base on the shell holds the shell rmly in its outer position so that it will not be moved inward by jarring the socket. In the bottom of the shell is a disk-shaped member I8 o1' insulating material having an opening I5 therein for the center terminal 9 of the socket. 'I'he disk I8 is held in place by spinning the shell against the outer edge ci the disk. Beneath the disk Ill extends a ange 20 of the shell which is adapted to make electrical contact with the contact II when the shell is threaded into the base. This contact is broken when the shell is threaded out of the base as shown in Fig. 3. When the shell is in the outer position, it is, therefore, electrically insulated from the conductors and the member I8 prevents contact with the center terminal 9 of metal particles such as tin foil which fall into the shell.

When the shell is in the outer position, it projects above the base but since in this position it is electrically insulated. there is no danger to the user.

Prior to inserting a lamp in the socket, the shell is in the position shown in Fig. 3. In the use of the socket the plug I8 of a lamp is threaded into the shell I. The plug is threaded into the shell until the friction between the threads on the plug exceeds the friction between the threads I3 on the shell and the threads |4a on the base. As soon as this condition obtains the shell is threaded into the base without further threading oi' the plug into the shell \mtil the shell reaches the position shown in Fig. 2. In this position contact is made between the ilange 24 on the shell and the contact Il in the base and the center terminal 3 in the base projects into the opening I 3 in the insulating member I3. Further turning of the plug I3 causes the plug to be threaded into the shell until it reaches the position shown in Fig. 2. In this podtion the center contact 2| oi the plug makes contact with the center terminal 3 of the base.

During the removal of the plug from the shell, the shell is iirst unthreaded from the base until it reaches the position shown in Fig. 3. This is due to the greater friction between the threads of the plug and the threads oi the shell. Alter the shell reaches the position-shown in Fig. 3, the plug is unthreaded from the shell to completely remove the plug from the socket.

In Figs. 6 and 6 is shown a socket having another arrangement for moving the shell into and out of the base as a plug is threaded therein. In this construction the base or husk 2| is a tubular part molded from suitable insulating material. In the upper end of the base is a cylindrical recess 22 in which is xed a disk 23 carrying spring contacts 24 and 25. The disk is pressed against a shoulder 23 at the bottom of the recess. 'Ihe contact 24 is located at the center of the disk 23 and is riveted thereto by a rivet 21 which also serves to secure a terminal 2l to the disk. The terminal 28 is located on the underside oi' the disk and is intended to be connected to a line conductor. The contact 2l is located near the periphery of the disk 23 and is riveted thereto by a rivet 3l which likewise secures' a terminal 3| to the underside of the disk. In the use of the socket, one of the line conductors is connected to the terminal 23 and the other line conductor is connected to the terminal 3|. The line conductors extend through an opening 32 in the lower end of the base 2l, and if desired; the space around the conductors and the terminals 23 and 3| may be iilied with a suitable cement to hold the conductors in place. 'I'he manner oi' connecting the line conductors to the terminals Il and 3| is not shown, it being well understood in the art.

Slidably mounted in the recess 22 is a sleeve I3 of molded insulated material in which is iixed a socket shell I4. The socket shell is provided with a flange 33 at its upper end which i'rictionaliy engages the side walls 3i of the sleeve and holds the shell therein. 'Ihe lower end of the shell 34 is closed by a disk 31 of insulating material which is held in place by a spunover flange I8 on the shell. The Bange 33 is above the contact 25 and is adapted to cooperate therewith to complete the electrical connection to the socket shell when the shell is moved inward from the position shown in Fig. 5. At the center o! the disk 3l is a rivet 33 which serves as the center contact or terminal of the shell, and when the shell is moved inward from the position shown in Fig. 5, makes an electrical connection with the contact 24. In the outside of the sleeve 33 is a groove 40 into which extends a pin 4| which is xed in the side wall of the base 2|. The pin 4| is ilxed in the base after the sleeve 33 has been assembled therein. It, therefore, serves to hold the parts in assembled relation. The pin 4| and the groove 40 also serve as a cam means for guiding the movement of the socket shell into and out oi the base as the sleeve 33 is turned relative to the base. When the shell is empty, the parts occupy the position shown in Fig. 5 in which ange 33 of the shell and the contact 39 are separated and therefore electrically insulated from the contacts 25 and 24 respectively. 'I'he socket is now protected from short- `circuit since there is nov electrical connection to shell 34 and the contact 31 which constitute the exposed terminals of the socket. In this position the pin 4| rests in a depression 42 in the groove 40. The depression 42 tends to hold the sleeve 33 in its outer position so that it may not be accidentally moved inward, for instance. by jarring of the socket. When a plug is threaded into the shell 34, the shell remains stationary until the friction between the threads on the plug and the threads on the shell exceeds the force required to turn the sleeve 33 relative to the pin 4|. The force required to turn the sleeve relative to the base is determined by the shape of the depression 42 which is chosen so that force due to friction between the plug and the shell exceeds the force required to turn the sleeve in the bese when the plug is partially threaded into the shell. As soon as this condition is reached, further turning of the plug causes the sleeve 33 to be turned relative to the base until the pin is in the vertical portion of the groove 44 after which an inward pressure on the plug will cause the pin to be moved inward until the contact 39 makes contact with the contact 24 and the ilange 3B makes contact with the contact '25. thus completing the electrical connection to the terminals or the socket. Further rotation of the plug causes the pin to be rotated to the end oi the upper horizontal portion of the groove 40, holding the shell stationary so that the plug, is threaded into the shell 34 until the center terminal of the plug makes contact with the contact 33, thus completing the electrical connection to the plug.

When the plug is turned to unthread it from the shell, the first effect will be to cause the sleeve 33 to be turned in the base so as to be moved outward. thereby breaking the circuit from the socket terminals to the contacts and 25. The outward movement of the sleeve 33 will be assisted by the force derived from the spring contacts 24 and 25. It is obvious that this spring means may be used. 'I'he outward movement of the sleeve may also be assisted by pulling on the plug as it is unthreaded. When the sleeve reaches its outer position, the pin 4| lits in the depression 42. In this position further rotation of the sleeve is prevented and continued turning of the plug will cause the plug to be unthreaded from the shell.

In Fig. 'l is shown another modification oi my invention. The greater portion of this socket is oi' the same construction as the socket shown in Figs. 1 to 4 inclusive and corresponding parts are denoted by the same reference numerals. In this construction accidental contact with the center terminal 9 is prevented by a spring 43. The spring 43 is integral with a disk 44 which rests in the bottom of a recess 45 in the base. On the upper side of the disk 44 is a disk 46 of insulating material over which extends a ange :incassa I1 on the contact il. The contact Ii therefore serves to hold the disks 4| and It in place. 0n the side walls of the recess Il is a helical pro- Jection Il which-cooperates with the external threads I! on a screw shell Il. The friction between the proiection 4l and the threads Il is less than the friction between the screw shell ll and a plug threaded therein so that the screw shell is moved into and out o! the base in the same manner as in the 'socket shown in Figs. l to 4 inclusive. Outward movement of the screw shell is limited by a iiange Il which engages a shoulder l2 on the base. When in its inner po-` sition a ange Il on the screw shell makes contact with the ilange 41 on the contact Iland the spring 4I projects through an opening Il in the bottom of the screw shell. 'When a plug is completely threaded into a .screw shell the center 'terminal of the plugengages the spring 4I and compresses it against the contact 0 thereby completing the electrical connection.

Prior to inserting a plug into the socket thel parts -occupvy the position shown in Fig. '1. In this position the electricaliconnectionto the screw shell it is broken and the spring I3 is separated from the contact l. Pieces of tin toil which may fall into the open socket are thereloreprevented short-circuiting the socket. When a plug, for example, the plug Ii, o! a lamp is threaded into the shell it turns relative to the shell until the friction betweenvthe threads on theplug and the threads in the shell exceeds Athe friction between the threads on the shell and the projection Ii. As soon as this condition is reached, the shell is threaded into the base without further turning of the plug relative thereto until the ange Il on the shell is rmly seated against the ilange I1 on the contact il. This completes the electrical connection to socket shell. Further turning oi the plug now causes the plug to be threaded into the shell until the cententerminal of theplug Il forces the spring into engagement with the contact l and completes the electrical connection to the plug.

During the removal o! the plugfrom the shell. the shell is ilrst unthreaded from the base until it reaches the position shown in Fig. '1. This is due tothe greater friction between the threads of the plug and the threads on the shell. After the shell reaches its outer position with its flange 5i against the shoulder l2, further turning of the lplug causes it to be unthreaded from the s el What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an electric socket, a base. a center terminal for co-operating with the center contact of a plug to be inserted in said socket. a screw shell rotatably and axially movable in the base, a part on the base engaging the threads on the outside ci the screw shell whereby the shell is moved into and out of the base upon' rotation therein, the friction between'said part of the base and the screw shell being less than the friction between the screw shell and the plug threaded therein whereby the shell may be rotated by the plug, means stopping outward movement o! the shell prior to disengagement oi' said part and the shell whereby the plug may be unthreaded from the shell, and a contact in the base engaged by the shell when the shell is threaded into the base. said contact being spaced from the shell when the shell is threaded out ci the base.

2. In an electric socket, a base, a center terminal for co-operating with the center contact oi.' a plug to be inserted 4in said socket, a screw shell rotatably and axially movable in the base,

cooperating parts on the screw shell and the base arranged to eiect axial movement ot the screw shell into and out oi the base upon rotation oi' the screw shell in the base, the resistance to rotation oi' the screw shell being such that the screw shell is rotated ln the direction to move it inward by threading the plug into the shell and such that the screw shell is rotated in the direction to move it outward by threading the plug out oi the shell. means stopping the outward movement of the shell prior toy disengagement oi' said parts whereby the plug may be unthreaded from the shell, and a contact in the base engaged by the shell when the shell is in its inner position, said contact being spaced from the shell when thev shell is in its outer position.

,f 3. In an electric socket, a base. a center terminal for co-operating with the center contact of a plug to be inserted in said socket, a screw shell rotatably and axlallymovable in thebase, cooperating parts on' the screw shell and the base arranged to eii'ect axial movement ol the shell into and out of the base upon rotation of the shell with respect to the base, said cooperating parts limiting the outward movement and rotation oi' the shell, and a contact in the base engaged by the shell when the shell is moved inward in the base, said contact being spaced from the shell when the shell is moved outward in the base.

nal and a screw shell comprising the other termina] olf the socket. a member movable to anV inner position permitting contact between the terminals of the socket and the terminals of a plugthreaded therein and movable to an outer position protecting the terminals of the socket from short-circuit, interengaging means whereby said member is moved to its inner and outer positions upon rotation relative to the socket,

said means being engaged when said member is in its outer position and serving to prevent rotation of said member, and means whereby the rotation of said member to move it to its inner and outer positions is effected by threading a plug into and out of the shell.

5. In an electric socket having a center terminal and a screw shell, a base. said Vshell and base having pin and slot means whereby the shell is movable into and out of the base upon rotation Vrelative thereto, and a contact on said base arranged to be engaged by said shell when the shell is in its inner position, said contact being spaced from the shell when the shell is in its outer position.

6. In an electric socket having a center terminal and a screw shell for cooperation with a plug threaded in the shell, a base, said shell and base having cooperating parts whereby the screw shell is moved into and out of the base upon rotation relative thereto, said parts being engaged when the shell is in its outer position and serving to prevent rotation of salti shell, the resistance to rotation oi the shell being less than the friction between the threads oi. the shell and the threads o1 a plug partially threaded therein whereby the shell will be moved into and out of the base by a plug threaded therein, and

when the shell is in its inner position. said contact being spaced from the shell when the shell is in its outer position.

7. In an electric socket having a center terminal and a screw shell, the shell and the pocket having cooperating parts whereby the shell is moved into and out oi the socket upon rotation relative thereto, said parts being engaged when the shell is in its outer position and serving to prevent rotation of said shell, the resistance to rotation of the shell being less than the friction between the threads of the shell and the threads c! a plug partially threaded therein whereby the shell will be moved into and out of the socket by a plug threaded therein, a member of insulating material carried by the shell for preventing short-circuit of the socket when the shell is in its outer position, said member permitting contact between the center terminal of the socket and the center contact of a plug threaded in the shell when the shell is in its inner position, and a contact engaged by the shell when the shell is in its inner position. said contact being spaced from the shell when the shell is in its outer position.

8. In an electric socket having a center terminal and a screw shell, the shell and the socket having cooperating parts whereby the shell is moved into and out oi the socket upon rotation relative thereto, said parts being engaged when the shell is in its outer position and serving to prevent rotation of said shell, the resistance to rotation of the shell being less than the friction between the threads of the shell and the threads of a plug partially threaded therein whereby the shell will be moved into and out of the socket by a plug threaded therein, a member of insulating material carried by the shell for preventing short-circuit of the socket when in its outer position, said member having a contact extendlng through the center thereof and adapted to make contact with the center terminal oi the socket and with the center contact of a plug threaded in the shell, said contact being spaced from the center terminal of the socket when the shell is in its outer position, and means for limiting the outward movement of the shell.

9. In an electric socket having a center terminal and a screw shell for cooperation with a plug threaded ln the shell, the shell and the socket having cooperating parts whereby the shell is moved into and out of the socket upon rotation relative thereto, said parts being engaged when the shell is in its outer position and serving to prevent rotation of said shell, the resistance to rotation of the shell being less than the friction' between the threads oi' the shell and the threads of a plug partially threaded therein whereby the shell will be moved into and out of the socket by a plug threaded therein, a member of insulating material at the bottom of the shell for preventing short-circuit oi' the socket when the shell is in its outer position, and means for limiting the outward movement of the shell.

10. In an electric socket having a center terminal and a screw shell for cooperation with a plug threaded in the shell, the shell and the socket having cooperating parts whereby the shell is moved intoand out of the socket upon rotation relative thereto, said parts being engaged when the shell is in its outer position and serving to prevent rotation of said shell, the reslsta'nce to rotation of the shell being less than the friction between the threads of the shell and the threads of a plug partially threaded therein whereby the shell will be moved into and out oi the socket by a plug threaded therein, and a contact engaged by the shell when the shell is in its inner position, said contact being spaced from the shell when the shell is in its outer position.

11. In an electric socket, a base, a center terminal for co-operating with the center contact of a plug to be inserted in said socket, a sleeve rotatably and axially movable in the base, a screw shell carried by said sleeve and movable therewith into and out of the base, cooperating parts on the sleeve and the base arranged to effect axial movement of the sleeve into and out of the base upon rotation thereof relative to the base, the resistance to rotation of the sleeve being less than the friction between the threads on the screw shell and the threads on the plug partially threaded into the screw shell whereby the sleeve is rotated in the direction to move it inward by threading the plug into the shell and whereby the sleeve is rotated in the direction to move it outward by threading the plug out of the shell, and a contact engaged by the shell when the shell is in its inner position, said contact being spaced from the shell when the shell is in its outer position.

12. In an electric socket, a base, socket termina'ls comprising a screw shell'and a center contact, said screw shell being rotatably and axially movable in the base, a part on the base enl gaging the threads on the outside of the screw shell whereby the shell is moved into and out of the base upon rotation therein, the friction between said part of the base and the screw shell being less than the friction between the screw shell and a plug threaded therein whereby the shell may be rotated by the plug, means stopping outward movement and rotation of the shell prior to disengagement of said part and the shell whereby the plug may be unthreaded from the shell, line contacts, means effective upon Inovement of the shell to its inner position for completing a circuit from one of the line contacts to one of the socket terminals, said circuit being open when the screw shell is in its outer position, and means connecting the other line contact and socket terminal.

13. In an electric socket, a base, socket terminals comprising a screw shell and a center contact, said screw shell being rotatably and axially movable in the base, cooperating parts on the screw shell and base arranged to effect axial movement of the screw shell into and out of the base upon rotation of the scre'.: shell in the base, the resistance to rotation of the screw shell being such that the screw shell is rotated in the direction to move it inward by threading a plug into the shell and such that the screw shell is rotated in the direction to move it outward by threading the plug out of the shell, means stopping the outward movement and rotation of the shell prior to disengagement of said parts whereby the plug may be unthreaded from the shell, line contacts, means eiective upon movement of the shell to its inner position for completing a circuit from one of the line contacts to one of the sockeL terminals, said circuit being open when the screw shell is in its outer position, and means connecting the other line contact and socket terminal.

14. In an electric socket, a base having a recess, socket terminals including a center terminal for co-operating with the center contact of a plug to be installed in said socket, and a screw shell, the screw shell being rotatably and axially einen 5 shell may be rotated by the plug, and a breakable electrical connection to one oi the socket terminais whereby the terminal is disconnected when in the outer and connected wh in the inner position.

JOSEPH D. CEADER.

CERTIFICATE 0F CORRECTION.

Patent lo. 2,158,852.

` JOSEPH D. CEADER.

It isrhereby certified that error appears inthe printed specification of the above nmnber-ed patent requiring eorrectionas fol line I4., clairs 7,V for the word I'poelset" read socket; and that the column lows: Page )4., first said Letters Patent should be read with this correction therein that the same may conform to the record of the cese in the Patent Office.

signed ann sealed this 11th any or July, A. D. 1959.

(Seal) Henry Van Arsdale Acting Ccmmissioner of Patents.

einen 5 shell may be rotated by the plug, and a breakable electrical connection to one oi the socket terminais whereby the terminal is disconnected when in the outer and connected when in the inner position.

JOSEPH D. CEADER.

CERTIFICATE 0F CORRECTION.

Patent lo. 2,158,852.

` JOSEPH D. CEADER.

It isrhereby certified that error appears inthe printed specification of the above nmnber-ed patent requiring eorrectionas fol line I4., clairs 7,V for the word I'poelset" read socket; and that the column lows: Page )4., first said Letters Patent should be read with this correction therein that the same may conform to the record of the cese in the Patent Office.

signed and sealed um 11th any or July, A. D. 1959.

(Seal) Henry Van Arsdale Acting Ccmmissioner of Patents. 

